1. Field of the Invention
The present invention relates to a photographic recording mamber having a semiconductive layer of a metal oxide, which is transparent and electrically conductive, on a polymer material. More particularly, the present invention relates to a member for photographic recording which possesses a remarkable antistatic effect even at low humidities.
2. Description of the Prior Art
Almost all polymer supports have surface resistivities of not less than 10.sup.13 .OMEGA.. With those supports which have surface resistivities of not less than 10.sup.13 .OMEGA. at room temperature and under ambient humidity, many problems occur during production or processing of these supports, or in using these supports as photographic film or as fabrics. For example, electrostatic charges are produced by friction and accumulate, causing discomfort due discharge of the accumulated electrostatic charge, adherence of dust, ignition of inflammable materials due to spark discharge, static marks (in a photographic film, the film is exposed by the discharge of the accumulated electric charge, forming spot-like or tree branch-like dots, which are designated static marks.), etc.
In order to prevent a charging of a polymer material which results in the above described various disadvantages, the following methods have hitherto been proposed.
1. A kneading method, in which an antistatic agent is previously incorporated in a polymer material. For example, organic compounds such as imidazoline type metal salts as described in Japanese Patent Publication Nos. 10326/1963 and 10327/1963, quaternary ammonium salts as described in U.S. Pat. Nos. 2,579,375, 2,836,517, Japanese Patent Publication No. 7366/1965, etc., and alkylarylsulfonic acid salts as described in U.S. Pat. No. 2,978,440, or metal compounds such as magnesium oxide as described in U.S. Pat. No. 2,758,984, zinc oxide and titanium oxide as described in U.S. Pat. Nos. 2,887,632, 2,940,941, and 3,062,700, and the like can be used.
2. A coating method, in which an antistatic agent is coated on a polymer material. For example, organic compounds such as alkylsulfonic acid salts as described in U.S. Pat. No. 2,614,984, quaternary ammonium salts as described in U.S. Pat. No. 2,876,127, polyvalent alcohols as described in U.S. Pat. No. 2,995,960, and the like, or metal oxides such as titanium oxide and tin oxide as described in Japanese Patent Publication Nos. 6616/1970 and 24890/1965, and the like can be used.
However, these methods have several disadvantages. For example, in the kneading method, no effect or only a slight effect is obtained unless a large amount of the antistatic agent is used. In the coating method, an organic solvent, which dissolves or swells the support must be used, and thus the planar surface of the support is deteriorated, or pollution based on the removal of the solvent and gases formed results.
Where organic antistatic agents such as alkylsulfonic acid salts, quaternary ammonium salts, and the like are used, the dependency of surface resistivity on humidity is large, and thus these organic antistatic agents have the defect that when the humidity is low, liberation of adsorbed water due to the dryness occurs, resulting in a remarkable decrease in the surface resistivity and in a loss of antistatic capability.
In those cases where metal oxides are used, since organic solvents are used in coating or kneading, problems of pollution due to the removal of the organic solvents occur. Furthermore, since these metal oxide particles form a layer in the form of a dispersion, the electrically conductive property of the layer is poor and the antistatic effect is small unless the amount of the metal oxide particles coated or kneaded is large. Moreover, the use of metal oxides is diadvantageous in that since these metal oxide particles are dispersed, the transparency of the layer is not good.
As described above, both the coating method and the kneading method have various disadvantages.
Recently, as a method free of the above described defects, the so-called vacuum vapor deposition method, in which a metal or a metal oxide is formed in a thin and uniform continuous layer without using any solvent, particularly a metal oxide, is deposited on a support in vacuum, has been proposed. A static charge preventing method comprising forming a deposited layer by vapor deposition, deposition of a metal for static charge prevention of an electron beam recording member is described in British patent specification No. 1,340,403 and U.S. Pat. No. 3,336,596, etc. Since this method is applied to an electron beam recording member, it is sufficient for the metal deposited layer provided to be permeable only to electron beams. In the electron beam recording member, the metal deposited layer need not be permeable to rays having a remarkably small energy as compared with electron beams, particularly visible rays which are important in the field of photographic light-sensitive members. That is, the metal deposited layer can be opaque at the stage of forming latent images. However, in general photographic recording members, particularly, negative films, movie films, X ray films, aero-films, and the like, in which transparency is essential, the deposited layer is not usable for these purposes unless it is transparent even though it possesses static charge prevention effect.
Attempts to use such a deposition method as a static charge prevention method for photographic recording members have now been made as disclosed in German Patent Application (OLS) No. 2,325,729, Belgian Pat. No. 799,893 and Japanese Patent Application (OPI) No. 51930/74. A method comprising forming a layer of a mixture of a metal and inorganic oxides as an intermediate layer between a polymer support and a photographic emulsion layer has been developed. In this case, an intermediate layer comprising 80 to 30% by weight of chromium, silver, nickel, or copper, alone or mixtures thereof, and 20 to 70% by weight of oxides of silicon, magnesium, tantalum, and the like, is provided as a static charge prevention layer. Of these metals, chromium is considered most excellent.
This method removes the above described disadvantages such as great variations in static charge prevention effect due to humidity where organic compounds are used, or opacity or unevenness where inorganic particles are used.
As is well known, however, chromium is quite harmful, and care must be taken in handling chromium. Chromium, copper, silver, nickel, and the like tend to be damaged by acid or alkali. Silver is quite costly and is not desired to be permanently used as an industrial product. Thus, this method is subject to various limitations from the standpoint of the starting materials employed. Furthermore, many difficult problems are encountered in the deposition procedures. That is, since a mixture is used, in this method, in preparing the intermediate layer, the deposition conditions of the mixture are quite complicated as compared with the deposition of a simple substance and even though the "flash method" or the "electron beam method" as described in L. Maissel and R. Glang, Handbook of Thin Film Technology, Chapter 1, McGraw-Hill, New York (1970) is used, it is quite difficult to provide a uniform and continuous deposited layer on a wide and long polymer support. As described above, prior art techniques have various problems.
On the other hand, as surface processings for the purpose of increasing the adhesion of the deposited metal to the polymer support, irradiation of electron beams onto the surface of the polymer support as described in, for example, G. M. Sessler, L. E. West, F. W. Ryan and H. Schonhorn, Journal of Applied Polymer Science, 17, 3199 to 3209 (1973), glow discharge as described in, for example, L. Holland, Vaccum Deposition of Thin Films, p.14, Chapmann & Hall Ltd., (1961), exposure of the polymer support to a plasma discharge atmosphere as described in, for example, Japanese Patent Application (OPI) No. 65271/1973, etc. are known. It is also well known that the surface of glass is, in general, cleaned by ion bombardment in a glow discharge atmosphere and the adhesion of the surface to the vapor deposited metal is increased, as described in, for example, Hakumaku Kogaku Handbook (Handbook of Thin Film Engineering), p. 1978, published by Ohm Co. (1964), and L. Maissel and R. Glang, Handbood of Thin Film Technology, 6-41, McGraw-Hill, New York, (1970), etc. However, it has not been known that the electrical conductivity of a vapor deposited thin film can be increased by applying surface activation processing onto the polymer material.